U.S. Frost Dates by Weather Station

NOAA station USC00355221 · Oregon

Frost Dates for Marion Forks Fish Hatchery, OR

NOAA weather station Marion Forks Fish Hatchery (USC00355221), Oregon · elevation 2475 ft (754 m) · hardiness zone 7b*

  • Lower-risk planting dateafter June 11only 1 spring in 10 still has a frost later
  • Typical last frostMay 1550% chance of a frost after it
  • Typical first fall frostSeptember 3050% chance of a frost before it
  • Frost-free season134 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season at Marion Forks Fish Hatchery, ORSpring: a frost after April 29 in 9 years out of 10, after May 15 in half of the years, after June 11 in 1 year out of 10. Fall: the first frost comes before September 10 in 1 year out of 10, before September 30 in half of the years, before October 18 in 9 years out of 10. Typical frost-free season: 134 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 15First frost ~Sep 30Frost season at Marion Forks Fish Hatchery, ORSpring: a frost after April 29 in 9 years out of 10, after May 15 in half of the years, after June 11 in 1 year out of 10. Fall: the first frost comes before September 10 in 1 year out of 10, before September 30 in half of the years, before October 18 in 9 years out of 10. Typical frost-free season: 134 days.JFMAMJJASONDLast frost ~May 15First frost ~Sep 30
frost likely chance fading 90% → 10% frost-free in a typical yearThe year at a glance. Blue: frost is likely; the gradient fades as the chance drops from 90% to 10%; green: the frost-free part of a typical year.

Frost dates (32°F)

Probability of frost, based on 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)June 11September 10
50% (typical)May 15September 30
90% (likely)April 29October 18
Frost-free season (32°F, 50% chance)
134 days
Hard frost (28°F), last in spring, 50% chance after
April 24
Hard frost (28°F), first in fall, 50% chance before
October 23

The last 15 years (2006–2020 normals)

Typical last frost May 12 (3 days earlier than the 30-year normal), typical first fall frost October 2 (2 days later). Frost-free season 142 days.

A shorter, more recent NOAA period. The 30-year normals above remain the main reference: 15 years carry more year-to-year noise.

Add these dates to your calendar Yearly reminders for the typical last frost, the lower-risk planting date and the typical first fall frost (.ics).

How the chance of frost changes with the date

Spring at Marion Forks Fish Hatchery: chance of a frost after this dateSpring, chance of a frost after the date: 10% June 11, 20% May 31, 30% May 25, 40% May 20, 50% May 15, 60% May 11, 70% May 8, 80% May 3, 90% April 29. Observed last spring frost in recent years: 2021 May 21, 2022 May 22, 2023 June 27, 2024 May 7, 2025 May 6, 2026 May 31.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1Jul 1Jun 11May 15Apr 292021: May 212022: May 222023: June 272024: May 72025: May 62026: May 31Fall at Marion Forks Fish Hatchery: chance of a frost before this dateFall, chance of a frost before the date: 10% September 10, 20% September 17, 30% September 21, 40% September 25, 50% September 30, 60% October 3, 70% October 6, 80% October 11, 90% October 18. Observed first fall frost in recent years: 2021 October 7, 2022 October 27, 2023 October 1, 2024 September 30, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Nov 1Sep 10Sep 30Oct 182021: October 72022: October 272023: October 12024: September 302025: October 6
Two charts, because spring and fall answer different questions: in spring, the chance that a frost still comes after a date; in fall, the chance that the first frost has already come before it. NOAA publishes these odds from 10% to 90%, so the lines stop there. ◆ marks the actual date in each recent year.

What actually happened in recent years

Observed dates of the last spring and first fall frost (32°F) at this station; ◆ marks them on the charts above
YearLast spring frostFirst fall frost
2021May 21October 7
2022May 22October 27
2023June 27October 1
2024May 7September 30
2025May 6October 6
2026May 31season not over yet

What these dates mean

The cautious fall date for finishing the harvest at Marion Forks Fish Hatchery is September 10, when there is only a 10 % chance that a 32 °F light frost has come earlier. In spring, the cautious date for setting out tender crops is June 11, a 10 % chance of a later frost. The 50 % date in spring, May 15, marks the point where the chance of a light frost later is even, while the 90 % date, April 29, is a gamble.

For gardeners, the 50 % dates—May 15 in spring and September 30 in fall—represent the median odds of a light frost occurring, giving a reference point for scheduling tasks. The hard-frost 50 % dates are April 24 and October 23; a hard frost at 28 °F can damage vegetation more severely than a light frost, so these dates are noted separately. The record spans 30 years and the two 32 °F 50 % dates are 134 days apart.

How to read the probabilities

The dates are probabilities from 30 years of weather, not a forecast for this year.

  • Spring: "10% after June 11" means that in about one spring out of ten a frost still happens after that date. The 90% date is the earliest: a frost after it happens in most years.
  • Fall: "10% before September 10" means that in about one fall out of ten the first frost arrives before that date.
  • 50% is the typical date: half of the years are earlier, half are later.
  • A light frost (32°F) damages tender plants; a hard frost (28°F) also stops most hardy vegetables.

Nearby weather stations

Map of weather stations near Marion Forks Fish Hatchery, ORNumbered nearest stations: 1 — near Warm Springs, OR — 35 mi; 2 — Three Lynx, OR — 36 mi; 3 — Lacomb, OR — 38 mi; 4 — near Sweet Home, OR — 38 mi; 5 — Stayton, OR — 44 mi.OR25 mi · 40 km1. near Warm Springs, OR — 35 mi12. Three Lynx, OR — 36 mi23. Lacomb, OR — 38 mi34. near Sweet Home, OR — 38 mi45. Stayton, OR — 44 mi5
  1. near Warm Springs, OR 35 mi (57 km)
  2. Three Lynx, OR 36 mi (57 km)
  3. Lacomb, OR 38 mi (61 km)
  4. near Sweet Home, OR 38 mi (62 km)
  5. Stayton, OR 44 mi (71 km)

Sources

* Hardiness zone 7b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 44.6125, -121.9486.